The present inventive system relates to fluid output measurement, and more specifically to an automatic urinary output measurement and recording mechanism.
In seriously ill patients, it is often necessary to measure the hourly urinary output. This output gives a great deal of information about the function of various body systems such as the cardiovascular system. If the blood pressure were to fall, the urinary output would diminish or cease depending upon the severity of the blood pressure drop. The kidney is very susceptible to damage during periods of anoxia, shock, severe trauma, bacterial infections or transfusion of incompatible blood. If the kidneys are seriously damaged, renal output may cease for periods of days to weeks before restoration. In addition, to assertain and manage the fluid balance of critically ill patients, it is necessary to know the extent of their urinary loss. If renal insufficiency ensues, this is usually detectable by a marked increase in the urinary output or a striking decrease in the urinary output. These two conditions have sometimes been designated as high output and low output renal failure. Sometimes the renal failure is merely functional and not pathological. Monitoring the urinary output alerts the physician when functional failure is not longer a threat. If urinary output falls beneath 30 cc's per minute, the situation is called oliguria. Oliguria may not respond to a simple increase in fluid intake by parenteral or oral route. Under these circumstances, the urinalysis may aid in determining whether the problem is simply one of under perfusion of the kidneys or of pathological damage. This can often be determined by sodium content of the urine. In patients with acute tubular necrosis, the urinary sodium levels are high while patients whose kidneys are simply under perfused have a low urinary sodium value.
One of the prime functions of the kidney is to concentrate the excretory waste material. To accomplish this, the kidneys must do osmotic work. Therefore, osmolarity of the urine is the best kidney function test that is available. It may be necessary to repeatedly follow the osmolarity of the urine to determine whether the kidneys are recovering and how seriously they are injured. Seriously damaged kidneys cannot produce urine with a osmolarity greater than 300 mil osmols per liter. In patients with elevated urea nitrogen levels and high urinary outputs, it is not uncommon to find that the kidney is unable to do osmotic work. If recovery occurs, urinary osmolarity rises and often diuresis ceases. In diabetic acidosis, it may be necessary to measure the hourly composition of the urine with respect to glucose and ketone bodies to make the necessary adjustments in insulin dosage and to determine the extent of recovery from the diabetic acidosis.
Urinary collection is usually done by inserting a catheter into the bladder and collecting the urinary output into a bag which is measured every hour and charted on the patient's records. This is, of course, not only time consuming and costly but it wastes personnel time. What is more important is that the time required to make accurate measurements exceeds the time available to do so and frequently the information required is not collected on an hourly basis. A number of mechanical devices have been made to allow measurement of the urine on an hourly basis, but the nurse must still make the measurement and dispose of the collection.